Big Dave

This was a replacement gear, and here's a picture of the original gear...can anyone tell if it's steel?

I have a variety of shims/washers I can use. The WSM says the shim should be 22x16x1. What do these measurements mean in English? 22mm diameter, 16mm hole, 1mm thickness?

Here's the old gear:

the flyin' scotsman

There should be a large difference in weight betwwen the alloy gear and a steel version plus the steel will attract a magnet.

Shim dimensions are outside diameter, inside diameter (hole size) and thickness; in metric millimeters.

Big Dave

Thanks. I think I might have kept the old gear, so I'll dig for it and compare weights.

Bill Ball

Dave:

Marc Thomas made it very clear to me that the replacement oil pump gears are steel and that is what he sold me. You got an Al replacement gear there, right? That should not be regardless of what the previous gear was. Somebody has some old stock Al gears and created a problem for you.

Big Dave

The gear was from an S4. Obviously I wasn't aware that there was a change. I don't know if the old one was itself a replacement. I've got records back to 1993, so I'll look.

Bill Ball

Oh, I see. At least the solution is clear, and you should be driving without a worry again in a few days.

Betting the old gear was steel, but if not, then the rear shim just got misplaced while the engine was apart. I always end up with extra parts after a job.

Big Dave

Update:

1. The oil pump gear is in fact ruined. I noticed that the inside of the gear has been widened by about 2mm. In the first picture, I've got a 17mm wrench spanning the opening, and you can see it's clearly wider than the wrench. The second picture shows my old gear with the correct diameter, narrower than the wrench. This is where all the metal shavings came from. The shaft is undamaged, inluding the threads.

2. My previous oil pump gear and the current one are different. The old gear is part no. 928 107 107 11, and the current one is 928 107 107 10. However, PET shows the proper gear to be 928 107 107 13. This is confusing.

3. The 22x16x1 shim IS still on the oil pump shaft. I didn't notice it before. This debunks the theory that a missing shim on an aluminum gear caused the nut to vibrate off.

4. The woodruff key vanished. I suppose it's possible that it was thrown free and lost. I know for a fact I didn't remove it during the rebuild. I have installed a new woodruff key, and it fits tightly.

5. The timing belt was punctured by the pump gear! Time for a new belt. See the pictures.

Everything is now clean, so I'll be ordering a new belt and pump gear this week. The new gear will go on with loctite and I'll make sure it's properly torqued. Barring complications ( ) I should be motoring again by Friday.

karl ruiter

I wonder if the belt was actually punctured by the woodruf key on its way to points distant.

Bill Ball

Eh, it was a good theory while it lasted. Now it looks like it just came loose. Not sure about the gear PNs except that 13 is probably the steel one that superceded the earlier aluminum one that came on 85MY. 13 is the only PN listed in 928 Specialists' PN database.

SharkSkin

Well Dave, it seems that your August '05 T-belt crisis is much milder than your August '04 T-belt crisis.

Big Dave

And I will be making an appropriate sacrifice to the 928 Shrine to assure that there is no August '06 T-belt crisis.

SharkSkin

Ah yes...

AO

Your intentions have been recorded.

Big Dave

Update:

The new oil pump gear and belt are on, and the car is running!

DonT

Way to go Big Dave...